1. Field of the Invention
The present invention relates to the field of trenchless tunneling by jacking or ramming pipe casing of large diameter over long distances, especially with respect to the installation of 100-400 feet of pipe casing which is larger than 72 inches in diameter.
2. Description of Related Art
There are various methods currently used to install underground pipe without digging trenches, commonly referred to as trenchless tunneling. These methods use pipe ramming and jacking, tunnel boring machines, or Micro-Tunneling.
Trenchless tunneling methods use tunnel boring machines (TBM) that include a boring shield that either pushes itself forward with completed extruded segments either made from precast concrete or bolted steel panels. Variation on the boring method has the TBM or mole mounted on or in front of the first casing pipe that is thereafter pushed into the formed tunnel with large hydraulic jacks. As these tunnel boring machines move forward through the ground, the soil is removed and typically mixed with a fluid and the mixture pumped out of the tunnel into a separation plant, wherein the solids are separated from the fluids. These methods do not work well in shallow applications, depending on soil type. A minimum industry standard requirement is a cover over the tunnel to be installed of at least two times the machine diameter. Tunnel boring is very slow and very expensive because of the type of equipment required.
TBM or Micro-tunneling involves underground trenchless tunneling in which energy is used to excavate the soil loose during the tunneling operation for soil removal. Again, Micro-tunneling is very slow in terms of the time required to create a tunnel and can be quite expensive
Trenchless tunneling methods that use pipe ramming or pipe jacking are known. The method typically uses a casing liner that is pushed underground into the tunnel by either a pneumatic ramming hammer, a set of hydraulic rams in tandem, or a combination of the two. The tunnel is typically started in a jacking pit that is dug to a depth to which a casing pipe or tunnel liner will be placed under the ground.
Capacities of currently employed ramming hammers and jacking pipe casing installations to date have been limited in capacity, such as total length or pipe size, requiring internal excavation as sections of pipe are installed in the tunnel. The ramming hammers and jacking rams have not had sufficient force for extended long tunnels with large diameters such as 6 ft. through 12 ft. for extended long tunnels above 100 feet because of the immense friction encountered as the pipe casing sections are formed and the entire casing gets longer and longer. By excavating concurrently with ramming or jacking, the risks of a tunnel cave-in or settlement of the face is a possible danger. The production process or the time required for installing the tunnel using jacking or ramming or a combination thereof is impacted by an interruption of having to excavate the pipe interior before another pipe section can be driven.
U.S. Pat. No. 5,632,575 issued May 27, 1997, describes a method and apparatus for controlled piping of bentonite around a pipe-jacked tunnel. Although this patent shows trenchless tunneling, it may use a combination of a tunnel boring machine or even tunnel excavation using hand labor. The system uses a tunnel ram and requires lubrication that presses the limit of the hydraulic jacking. This is a completely different operation than pile driving a tunnel casing great lengths using a horizontal pile driver.
U.S. Pat. No. 4,391,553 issued Jul. 5, 1983, shows a hydraulic control system and method of controlling the operation of tunneling apparatus. This shows the conventional use of a pair of hydraulic rams and pumps. This system is severely limited in total pipe casing achievable distances and operates completely differently than Applicant""s invention.
U.S. Pat. No. 4,557,672 issued Dec. 10, 1985, shows an apparatus and method for tunnel construction with shield drive. Again, this is a trenchless tunneling method that is completely different than Applicant""s invention. This method uses a shield drive and incorporates a concrete tunnel lining directly behind the shield. This is very slow and expensive.
U.S. Pat. No. 3,742,718 issued Jul. 3, 1973, shows a tube driving apparatus for driving large diameter tubes where a limited amount of space is available. The method and apparatus shown are severely limited in the total trenchless pipe distances available of the tube construction, which is completely different than that disclosed by Applicant""s invention.
U.S. Pat. No. 4,398,845 issued Aug. 16, 1983, shows a tunnel driving apparatus that incorporates a cutter shield with a plurality of drive members in a side-by-side, cylindrical array. This system is completely different than that employed by Applicant.
The subject of the present invention overcomes the problems discussed above by providing a method and system that uses a powerful pile driving hammer, like those used for offshore vertical pile driving construction, that greatly increases the length of a trenchless tunnel casing to be driven while greatly reducing the risk of cave-in. With existing jacking/ramming systems, as more tunnel liner sections are installed, the friction between the liner sections and interior and exterior surface and the surrounding soil increases. Due to the limited driving capacity of these systems, this phenomenon requires the interior plug to be removed as each tunnel section is added in order to reduce the upper pushing limit of the typically used jacking equipment.
There is a need for a method and apparatus that has sufficient driving force to drive large sections of tunnel casing, or even the entire tunnel casing, before excavation of the soil plug begins in order to improve safety and production and also allow greater diameter pipe and longer drive lengths in one continuous operation without excavation, thereby reducing the risk of collapse of the face or settlement of the ground. This is important since typically, these installations underground are often planned under busy roadways or railroads (or a combination of both), whereby it is not practical or cost effective or even possible to open cut with open trenches. Thus trenchless tunneling is extremely important in certain environments. With the present invention, the Applicant can use trenchless tunneling to drive underground pipe casing over 72 inches in diameter and up to 168 inches for distances exceeding 100 feet. This can also be done very quickly in a matter of hours instead of days and weeks compared to other methods of trenchless tunneling at greatly reduced cost.
The use of an impact piling (pile driving) hammer (such as a modified Hydrohammer manufactured by IHC) that uses low frequency and high velocity and high energy is preferred over the use of a low energy, low velocity, and high frequency system, such as ramming, in that the soil particles are forcibly sheared with the former and not simply brought in suspension as with the latter. The limitations of pipe ramming/jacking are especially evident for installation done in damp or fluid-bearing soils where the pneumatic ramming can lead to soil liquification that can cause the soil plug to run.
Another advantage of the large capacity available with the low frequency and high velocity and high energy system in accordance with the present invention using a piling hammer is that on particularly environmentally sensitive projects, a hammer of sufficient driving capacity can be chosen so as to eliminate the need to lubricate. Thus, in certain environmental situations, the system avoids environmental contamination when the installation, for example, is near or over fish-bearing creeks. However, if lubrication is permitted, it also allows for even more increased distance that can be obtained using the pile driving hammer in accordance with the present invention.
A trenchless tunneling system and method for driving horizontally placed large pipe casings that are joined sequentially together in sections to form a tunnel which is safer and more efficient over current methods. The present invention can provide for the creation of a tunnel using casings of large diameter (over 72 inches) for great lengths (exceeding 100 feet) without digging a trench.
One objective of the invention is to provide a method and system or installation of pipe casings in areas where open cut excavation is not possible or practical, such as under heavily traveled roads, highways, railroads, or any combination thereof.
Another advantage of the large capacity availability with the low frequency and high velocity and high energy system is that on particularly environmentally sensitive projects a hammer of sufficient capacity may be chosen in accordance with the present invention to eliminate the need to lubricate with bentonite or other additives, avoiding environmental contamination.
Another object of the invention is to provide a hammer of sufficient capacity that on less environmentally sensitive projects, especially where tunnel distances are required exceeding 300 feet trenchless, the invention can provide a method and apparatus for providing lubricant, such as bentonite, on the inside or outside or both, for great distances.
And yet another object of the invention is to provide a method that temporarily stabilizes soil at the entry phase of the casing pipe to be installed whenever the entry of the installation is near the shoulder of a road, a railroad embankment, or other structure requiring settlement avoidance.
It is very important that a temporary means of soil support is provided at the leading open end of the pipe as soon as the drive is started to avoid collapse of the soil into the pipe, resulting in loss ground and surface settlement. A temporary seal made up of interlocking steel plates against the cutting shoe form an enclosure at the front end, thus a temporary bulkhead, whilst at a variable distance, dependent upon the soil type to be tunneled, a temporary bulkhead is placed inside the casing to be driven in such a way that the space between the two bulkheads can then be filled with a flowable fill. The rear bulkhead is constructed out of aluminum, and is a shield that uses an inflatable rubber seal of which the friction between the interface with the internal diameter of the casing pipe may be controlled by means of regulating the pressure in the inflatable seal; this bulkhead together with the flowable fill plug forms a controllable resistance that will support the face upon entry, thereby avoiding surface settlement.